Blow molding is a process commonly used for producing hollow plastic objects. A typical blow molding operation involves mold halves which are closed about an extruded parison of warm plastic and the introduction of air into the closed-off parison to cause same to conform to the shape of the mold cavity. After the plastic has cooled, the mold halves are separated to release a molded product. The mold halves are typically provided with interior conduits through which heat carrying medium is circulated, to heat or cool the mold as necessary in the particular application.
Containers for consumer products are often provided with features such as finishes (threaded necks which receive caps) and “push-ups” or “Champagne” bases (hollows formed in the bases of the containers to provide stability). Historically, portions of the mold halves which define these features in the finished container are defined by inserts which are machined separately from the remainder of the mold and then secured thereto.
Inserts are also used to apply details such as dates, logos and codes to the surface of the molded product, to achieve small variations in the shape of the molded product without the requirement of manufacturing an entirely new mold and, when machined out of harder material than the remainder of the mold, to provide enhanced wear resistance to portions of the mold that can benefit therefrom.
By segmenting the mold halves, mold cavities of very complex shapes can be routinely constructed using conventional three-dimensional milling machinery, as is generally available in mold-making shops.